1. Field of the Art
The present invention relates to a potentiometer, and, more particularly, to a potentiometer used in a device that experiences mechanical vibrations.
2. Background of the Prior Art
Potentiometers are used, for example, as measuring transducers or sensors in control or regulation systems in which the position of a movable element is sampled and the potentiometer then furnishes an electrical output signal which is proportional to the position sensed. Such a potentiometer, for instance may be used to sample the position of a throttle valve in an internal combustion engine.
In those cases, the potentiometer is fastened to another object, such as being fastened directly at the engine block of an internal combustion engine. As a consequence, the potentiometer receives all movements, especially vibrations of the other object. It was found with diesel engines, for example, that a potentiometer directly flange-connected to the engine block is subjected to accelerations of up to 300g (g=acceleration due. to gravity). Due to the mass inertia of the components which are movable with respect to each other and the potentiometer, especially the mass inertia with respect to the slider, such accelerations cause the slider to oscillate with respect to the resistor path on the resistor plate, and that will result in the abrasion of the resistor layer. Tests made with conventional potentiometers which were flange-connected to a diesel engine have shown that the resistor layer was rubbed down in no more than 3 to 4 hours. The potentiometer then could no longer be used.
It has been attempted to solve the above described problem by providing damped support for the entire potentiometer with respect to the engine block, such as by bolting it to the engine block with rubber buffers in between. However, the desired longer service life was not achieved by that measure and also turned out to be rather costly. Also, adjustment of the potentiometer was expensive because any tightening of the fastening screws necessarily caused deformation of the rubber buffers, thereby changing the relative positions of the potentiometer and the engine block, and causing nonalignment requiring further adjustment. In other words, the electrical output signal of the potentiometer depends on the force by which the fastening bolts are tightened. The sealing of the engine block with respect to the potentiometer likewise causes difficulty.